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• Vendrasco, MJ.
• Checa, A
• Heimbrock, WP.
• Baumann, SD.J.
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• Vendrasco, MJ.
• Checa, A
• Heimbrock, WP.
• Baumann, SD.J.
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• Vendrasco, MJ.
• Checa, A
• Heimbrock, WP.
• Baumann, SD.J.

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Geosciences 2013, 3(1), 1-29; doi:10.3390/geosciences3010001

Article

Nacre in Molluscs from the Ordovician of the Midwestern United States

Michael J. Vendrasco ^1,* , Antonio Checa ² , William P. Heimbrock ³  and Steven D.J. Baumann ⁴

¹ Department of Biological Science (MH-282), California State University, Fullerton, CA 92834, USA ² Department of Stratigraphy and Palaeontology, Faculty of Sciences, University of Granada, Avenida Fuentenueva s/n, Granada 18071, Spain ³ Dry Dredgers, 1621 Westwood Avenue, Cincinnati, OH 45214, USA ⁴ Midwest Institute of Geosciences and Engineering, 2328 West Touhy Avenue, Chicago, IL 60645, USA

* Author to whom correspondence should be addressed.

Received: 13 November 2012; in revised form: 24 December 2012 / Accepted: 31 December 2012 / Published: 8 January 2013

(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)

Download PDF Full-Text [7072 KB, uploaded 30 January 2013 09:37 CET]

Abstract: Nacre was previously thought to be primitive in the Mollusca, but no convincing Cambrian examples are known. This aragonitic microstructure with crystal tablets that grow within an organic framework is thought to be the strongest, most fracture-resistant type of shell microstructure. Fossils described herein from the Ordovician of Iowa, Indiana, and Ohio provide supporting evidence for the hypothesis that sometime between the middle Cambrian and late Ordovician, nacre originated in cephalopod, bivalve, and possibly gastropod lineages. The correlation of independent origins of fracture-resistant nacre with increasing shell-crushing abilities of predators during the Cambrian-Ordovician suggests an early pulse in the evolutionary arms race between predators and molluscan prey.

Keywords: nacre; Ordovician; Isorthoceras; cephalopod; shell microstructure; Maquoketa; Arnheim; Cyclora; Ohio; Iowa

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